If your sent emails are not appearing in Copper, it could be due to several things. Please confirm the following:
1: The Chrome Profile User is the same Gmail account and your Copper account.
2: The Copper Chrome Extension is loaded in the chrome browser and is logged using the same Gmail account as Copper.
This should enable the emails to be synced normally.
If you now have emails that are not in Copper. This can be solved by triggering the sync with a change to the email address. Copper syncs the emails whenever a new email address is discovered. To resync previous emails, do the following:
1. Find the contact in Copper.
2. Change their email address, eg: Add a + before the first letter or Remove the last letter of their email and press Enter to update (for example firstname.lastname@example.org ⇨ email@example.com)
3. Now change it back to the original email address
This should now trigger a refresh of the email sync. Please Note: This may not work in all situations.